This research is directed at the isolation and identification of the human aniridia gene. Aniridia, an eye disease, results in progressive loss of vision and is frequently accompanied by absence of the iris and changes in the optic nerve. Isolation of the gene for aniridia is important for several reasons: (a) it is necessary in understanding the molecular basis of the disease; (b) it will be useful in identifying individuals at risk for disease; (c) the severity of the disease may be correlated with the position of mutation in the gene i.e., change in levels of gene expression or changes in specific domains of the aniridia protein. Knowledge of the molecular structure of the gene should be very useful in classification of aniridia patients and future therapy. Using the physical map location in band pl3 of human chromosome 11 as a guide we used positional cloning to isolate a candidate gene for the aniridia locus. The message encoded by the gene is 2.7 kb in size and is present in the eyes and brain, both during the fetal and adult stages. Our objective is to determine the structure of the AN gene, deduce the protein encoded by it and its potential function. In extending this research to patients, we will search for mutation in the aniridia gene in affected individuals and determine if mutations in specific protein domains correlate with subtypes of the clinical disease.